/Engine/Source/Runtime/Engine/Classes/Kismet/BlueprintSetLibrary.h
Assigns Result to the union of two sets, A and B. That is, Result will contain all elements that are in Set A and in addition all elements in Set B. Note that a Set is a collection of unique elements, so duplicates will be eliminated.
static void Set_Union ( const [TSet](API\Runtime\Core\Containers\TSet)< int32 > & A, const [TSet](API\Runtime\Core\Containers\TSet)< int32 > & B, [TSet](API\Runtime\Core\Containers\TSet)< int32 > & Result )